When was the diesel engine invented?    The diesel engine uses a four-stroke combustion cycle just like a gasoline engine. The four strokes are: Intake stroke -- The intake valve opens up, letting in air and moving the piston down. Compression stroke -- The piston moves back up and compresses the air. Combustion stroke -- As the piston reaches the top, fuel is injected at just the right moment and ignited, forcing the piston back down. Exhaust stroke -- The piston moves back to the top, pushing out the exhaust created from the combustion out of the exhaust valve. Remember that the diesel engine has no spark plug, that it intakes air and compresses it, and that it then injects the fuel directly into the combustion chamber (direct injection). It is the heat of the compressed air that lights the fuel in a diesel engine. Some diesel engines contain a glow plug. When a diesel engine is cold, the compression process may not raise the air to a high enough temperature to ignite the fuel. The glow plug is an electrically heated wire (think of the hot wires you see in a toaster) that heats the combustion chambers and raises the air temperature when the engine is cold so that the engine can start.  Why do big diesel engines and race car engines have such different horsepower ratings? What's the best way to increase horsepower? What's the difference between gasoline, kerosene, diesel, etc? Why do big diesel engines and race car engines have such different horsepower ratings? The answer to your question has to do with the way the two engines are designed. Your 11 liter diesel engine has a long stroke. That means that the piston is traveling a relatively long distance up and down in its cylinder on each cycle. A racing engine, on the other hand, has a short stroke. The piston in a racing engine has a large diameter for the engine size, and it goes up and down a relatively short distance on each cycle. This means that a race car engine can run much faster -- up to 15,000 RPM in a __________ engine -- but has relatively little torque. A large diesel engine usually cannot get above 2,000 RPM, but has huge torque because of the long stroke. The torque is what lets your engine pull a huge load up a hill. So why does an engine with huge torque and low maximum RPM get a low horsepower rating? Imagine taking 33,000 foot-pounds and walking it around in a circle rather than a straight line. For example, if you took a 10 foot pole and attached it to a vertical axle, the circumference of its circle is: circumference = 10 * 2 * pi = 62.8 feet If one horse is pushing on the pole with 100 pounds of force (1,000 foot-pounds of torque), it can move the pole at 5.25 RPM. Torque and horsepower are directly related to each other. You can see from the horsepower equation that high RPM values favor horsepower. If you take an engine with a certain torque and run it at very high revs, it can generate lots of horsepower even though its torque hasn't changed at all. A racing engine can produce relatively low torque, but because it can rev so high it gets a great horsepower rating. A big diesel has huge torque, but "gets no respect" in terms of horsepower because it cannot ever get above 2,000 RPM. This "makes sense" -- if two engines produce the same torque, the one that can do it more times per minute does more work and therefore has more power. The difference in maximum RPM ratings also tells you why trucks need so many gears. A race car engine might idle at 1,000 RPM and can accelerate to 15,000 RPM -- a multiplier of 15. A big diesel might have a multiplier of only 2 or 3. Because the RPM range between minimum and maximum is so small on a diesel, there needs to be lots of different gears to keep the engine in its productive RPM range at any speed. That 5,252 number, by the way, comes from dividing 33,000 by (2 * pi). Imagine taking 33,000 foot-pounds and walking it around in a circle rather than a straight line. For example, if you took a 10 foot pole and attached it to a vertical axle, the circumference of its circle is: circumference = 10 * 2 * pi = 62.8 feet If one horse is pushing on the pole with 100 pounds of force (1,000 foot-pounds of torque), it can move the pole at 5.25 RPM. Torque and horsepower are directly related to each other. You can see from the horsepower equation that high RPM values favor horsepower. If you take an engine with a certain torque and run it at very high revs, it can generate lots of horsepower even though its torque hasn't changed at all. A racing engine can produce relatively low torque, but because it can rev so high it gets a great horsepower rating. A big diesel has huge torque, but "gets no respect" in terms of horsepower because it cannot ever get above 2,000 RPM. This "makes sense" -- if two engines produce the same torque, the one that can do it more times per minute does more work and therefore has more power. The difference in maximum RPM ratings also tells you why trucks need so many gears. A race car engine might idle at 1,000 RPM and can accelerate to 15,000 RPM -- a multiplier of 15. A big diesel might have a multiplier of only 2 or 3. Because the RPM range between minimum and maximum is so small on a diesel, there needs to be lots of different gears to keep the engine in its productive RPM range at any speed. What's the difference between gasoline, kerosene, diesel, etc? Here are further guidelines. A gasoline engine is a stoichiometric engine, which uses an efficient combination of air and fuel for total combustion. It intakes a mixture of gas and air, compresses it and ignites it with a spark (spark ignition). Most gasoline engines run in light duty vehicles such as passenger cars and small trucks. A diesel engine is a heavier duty product designed for work in industrial, automotive, and truck applications. It takes in only air at the beginning of the cycle, compresses it and then injects fuel into that compressed air. The heat of the compressed air lights the fuel spontaneously. So diesel engines operate with compression ignition (no spark plugs). The compression of fuel and air is at a much higher compression ratio, which results in better efficiency and higher power. Diesel Engine Problems I am often asked to diagnose vehicle problems over the phone, if only it was that easy. Main Dealers, specialists and garages equipped with expensive and sophisticated diagnostic equipment still seem to struggle. Computer generated fault codes only go a certain distance to point in the direction of the problem. After that, it is a process of elimination, unfortunately at your expense. The innovation of the computer generated fault diagnosis has led to a generation of mechanics that have often lost sight of the basic operating principles of the diesel engine. Unfortunately the fault codes don’t always pin point the problem but rather bring up an array of codes that could be either this or that. Being told: ’we have tried this and it has not helped’ or the best one, ‘sorry there are no fault codes so we can’t find anything’, is extremely frustrating and can be costly. I am not knocking the modern mechanic, nowadays diesel engines are extremely sophisticated and difficult to diagnose. I personally do not have any diagnostic equipment and all my knowledge comes from other people’s experiences and years of working in the diesel trade. I hope that the information below helps and does not just confuse you but at least it is something to start with and has not cost you anything. Diesel: Troubleshooting
Low compressionLow engine compression will result in insufficient heat being generated to ignite the fuel and cause hard starting. This is more of a problem with older or high mileage vehicles. To find out the compression perform a cold engine compression test. Compression should be between 20 to 35 bars or 300 to 500 PSI. Anything below this will cause starting problems. Low fuel pressureIt is in this area that most fuel supply problems occur. The problem could either be poor fuel supply to the rail/injectors or the rail/injectors are not holding the fuel within the system. The best way to diagnose this is to look at the fuel supply in 3 areas.
Low cranking speedIf the engine turns over too slowly, the pump cannot generate enough fuel pressure to activate start of injection causing hard starting problems. This is usually seen more in the colder months especially if the battery is run down. Glow plugs or relay faultyThe engine relies on the glow plugs to generate heat to help with the combustion cycle. Some engines only use the glow plugs when cold but others will allow the glow plugs to work when the ECU (vehicle’s computer) needs them to be on to help with combustion. Problems in this area will cause diesel engine starting problems, uneven running and white smoke when the engine is cold. Insufficient fuel supplyThis speaks for itself, not enough fuel in the tank or a problem with supply pipes being cracked or bent. The fuel tank breather can sometimes be blocked causing a vacuum in the tank which in turn draws the fuel back to the tank. Fuel quality – contaminationI have been involved with diesel fuel injection all my working life and still find the topic of fuel and additives controversial. Working with diesel injectors we see the result of poor fuel quality - damage and condition of the internal components. I know that if a good quality diesel and an additive is used regularly it will prolong the life of diesel injection equipment. Poor fuel quality and general wear and tear are not the only cause of injector failure, the newer type of injectors sometimes fail due to design problems. I would estimate that about 85% of injectors fail due to fuel related issues and the balance due to design problems. Air - Vacuum in fuel supply and Blocked fuel supplyThis is similar to "insufficient fuel supply" but dirty fuel filters or a faulty filter head assembly may also cause fuel supply issues and hard starting. Faulty injector/sProbably the biggest result of injector failure is due to the injectors having excessive return flow or back leakage. This is due to worn parts which allow excessive fuel to go through the diesel injector and to return back to the tank or fuel system. This causes a drop in rail pressure (see "low fuel pressure") which results in hard starting or not starting at all. Another problem resulting from worn parts is a delay in the start of injection which in turn results in rough running at low RPM or your diesel not starting. Faulty high pressure pumpIf the pump is faulty there will be a "low fuel pressure" problem. This problem arises if the pump "breaks up" internally causing swarf and iron filings to get into the fuel system. Normally this causes damage to the diesel injectors and unless the complete fuel system is attended to the problem will arise again. This is an expensive failure and no short cuts can be taken. Faulty pressure regulator – sensorMost vehicles have a pressure regulator fitted on the high pressure pump and a sensor fitted on the rail. If either of these are faulty there will be running issues like hard starting, uneven tick over and the vehicle cutting out when the RPM is increased. Faulty low pressure pumpNot all vehicles have a low pressure supply pump but if they do it can be found either in the tank or on the fuel pipe near the tank. If your low pressure pump is faulty, you may experience symptoms similar to those of a "faulty high pressure pump". Air intake restrictionThis would be due to a dirty air cleaner, blocked pipes or a stuck butterfly valve found on some vehicles. In addition, a faulty air flow sensor on the air intake will cause problems running and excessive smoke. Turbo problemsWe are seeing more turbos failing with newer vehicles, I put it down to a combination of things, high revving engines demanding more power, incorrect driver actions(not allowing the engine to idle a while when started and before switching off), poor maintenance and not replacing old oil with a good quality oil. A turbo spins at about 42000 revolutions per minute, the average washing machine at 1000 rpm. As vehicles get older the turbo waste gate sticks causing the vehicle to either shut down, go into limp home mode or smoke excessively. If a vehicle has a variable vane turbo, problems can arise if the vans carbon up, the symptoms are lack of power, black smoke and hesitation on acceleration. Also make sure that all the vacuum pipes and sensors that operate the turbo are operating correctly. Another problem is if the air pipes to and from the inlet, inter cooler and turbo leak due to damage or loose clamps , the vehicle can experience similar problems. EGR problemsI do not know why EGR (exhaust gas recycling) valves were ever put onto diesel engines, they cause more trouble than they are worth. The idea is that whilst the engine is at tick over, a valve opens and allows some of the exhaust gases to pass back into the nice clean air intake manifold. After a while the gases containing dirty, sooty carbons start to cover and coat the intake area and valves causing the air to fuel ratio to become unbalanced thus resulting in more black smoke being emitted from the exhaust. This black smoke is then drawn back into the air intake via the EGR valve. A vicious cycle then starts with the engine producing more smoke and sootier carbons being drawn into the intake, a major problem. I would always recommend the EGR valve to be blanked off but some vehicles will not allow this. Injector blow–by, seat leakingInjector "blow-by" can be the cause of some of the following symptoms. Hard or difficult starting / erratic or uneven tick over or idle / lumpy running / smoke on tick over or acceleration / black tar around the injectors and a chuffing sound from the engine when running. Injector "blow-by" occurs when the injector does not seal against the injector seat in the cylinder head. Often a chuffing sound is heard or black "tar" can be seen around the injectors. On some engine applications if this continues serious engine damage could result due to the fact that the ECU will over compensate the fuelling on the cylinder or cylinders with the seating problem causing piston washing or cylinder over fuelling. Even if the injector is removed, cleaned, a new copper washer fitted and then replaced it will not always rectify the problem. The reason for this is that the seat in the cylinder head has been eroded by the escaping combustion gases resulting in damage to the seat. The only way to reface the seat is to use a seat cutting tool and gently reface the seat in the head. More info can be found at http://www.uniteddiesel.co.uk/tips-troubles.php. Cam – crank sensorCheck that the sensors are not loose, cracked or damaged as they are not very expensive. If you have any doubts I would recommend replacing them. Injector wiring harnessMore of a problem with vehicles that have the injectors under the rocker cover and allow oil to come in contact with the electrical connections. Even though some diagnostic machines will condemn the injector/s, many times the fault lies with the wiring harness. Check that the electrical connections on the injectors are good and are making contact. Internal engine problemsThis is generally mechanical failure such as problems with bearings, pistons, oil pressure, overheating, valves and more. The list is endless, it is best to get an engine specialist to diagnose the fault. The Answer is in the SmokeWe can generally understand what is wrong with a diesel engine by the colour of smoke emitted from the exhaust. There are three basic colours - black, white and blue. Black SmokeThis is due to a air to fuel ratio imbalance, either the fuel system is delivering too much fuel into the engine or there is not enough clean air (oxygen ) a few things to look for :
White SmokeNormally means that the fuel injected into the cylinder is not burning correctly. The smoke will burn your eyes.
Blue SmokeThe engine is burning engine oil
http://www.uniteddiesel.co.uk/diesel-engine-smoke.php |